NEW YORK — If the New York Yankees are going to earn a 14th consecutive playoff berth, they'll have to do it without Jorge Posada.

The five-time All-Star catcher will have season-ending surgery on his right shoulder, ending his attempt to return to the lineup for New York's postseason push.

Posada has struggled with shoulder pain most of the season, weakening his throws and limiting his playing time behind the plate.

On the disabled list for the second time this year, Posada was trying to rehabilitate his shoulder enough to come back as a DH or first baseman this season. But after the Yankees acquired outfielder Xavier Nady in a trade with Pittsburgh on Saturday, they determined it was best for Posada to have surgery now, general manager Brian Cashman said today.

"It's just the obvious way to go," Cashman explained.

Posada is expected to be sidelined at least six months and it's not certain that he'll be ready for the start of spring training in February, Cashman said.

"As difficult as it is, I can focus on coming back 100 percent for next season instead of coming back at less than that now," Posada said in a statement. "Until then, I still plan on being a teammate and friend to the guys I share this room with. I may not be playing, but I want to be a part of this team and the run that we're on."

The Yankees won their first eight games after the All-Star break before losing Sunday night in Boston. They entered today three games behind first-place Tampa Bay in the AL East and two back of the Red Sox.

New York announced the decision after Posada met with Cashman and manager Joe Girardi following batting practice. Cashman also spoke to co-chairmen Hank and Hal Steinbrenner to "make sure that they were all on board."

"After speaking with Brian and Joe, we thought it was best for me — and the team — to have the surgery now," Posada said. "I've always taken pride in being there for my team and playing every day with them. With Xavier here now, there isn't as much pressure on me to return."

Posada took some light swings from the left side during batting practice Monday before New York played the Baltimore Orioles. Earlier in the afternoon, he said he still hoped he was in the team's plans for this season.

No date has been set for the operation, Cashman said. It will be performed by New York Mets medical director Dr. David Altchek, a shoulder specialist who examined Posada last week.

An MRI showed fraying in the tendons around the labrum, but not a rotator cuff tear, Posada said then.

"The reason we were going through the process that we did before was basically we didn't have someone to slot right in there as a hitter. Now we do with Xavier Nady. So it gives us the opportunity to move forward with Jorgie," Cashman said. "He was willing to do what we wanted when there was a need, so he was delaying the surgery through that need. But now that we have a hitter, I think this was predictable."

Posada reached the majors in 1995 and never went on the DL until this season. He was hitting .268 with three homers and 22 RBIs in 51 games this year. A longtime Yankees backbone, the 36-year-old catcher signed a $52.4 million, four-year contract in the offseason.

With Posada injured, defensive whiz Jose Molina is getting most of the playing time behind the plate. Cashman doesn't think any enticing catchers will be available as Thursday's trade deadline approaches.

"We're planning on going with what we've got," he said.

Hideki Matsui still hopes to put off season-ending surgery and return from a swollen left knee that has sidelined him since June 23. Wearing a new brace on his knee, the designated hitter-outfielder took 20 swings off a tee and five soft-toss cuts on Monday.

If all goes well, Matsui thinks he could begin playing minor league rehab games in a week or two.

"I think so far it's looking pretty good," he said through a translator.

The Yankees would like to add a starting pitcher before the trade deadline, but Cashman said he wasn't close to a deal.

"Right now it's frigid out there," he said.

Hal Steinbrenner said the Yankees would be willing to add payroll if necessary in order to make a trade that would help.

"It would not be something that stands in our way, but it doesn't mean the right guy is out there," he said.

In other injury news, right-hander Phil Hughes (broken rib) had his first rehab start with the Gulf Coast League Yankees postponed by rain. Now, he and Carl Pavano (elbow surgery) are each scheduled to throw two innings or about 35 pitches Tuesday for Class-A Charleston.